Method and apparatus for humidifying inhalation mixtures



Nov. 1, 1966 J M. WALKER, JR 3,282,266

METHQD AND APPARATUS FOR HUMIDIFYING INHALATION MIXTURES Filed Aug. 2;1962 FIGI from 2! 20 Oxygen Supply 23 27 29 Hi 1 f. j 25 I0 IT24 32Power 34 mpg I I I 35 W I 32 l (l H62 Q51 [Q :3 @Jo I! INVENTOR. JOHN M.WALKER,JR.

A TTORNE Y S United States Patent 3,282,266 METHOD AND APPARATUS FORHUMIDIFYING INHALATION MIXTURES John M. Walker, Jr., Langhorne, BucksCounty, Pa. Filed Aug. 2, 1962, Ser. No. 214,393 14 Claims. '(Cl.128-209) The present invention relates to an improved method andapparatus for nebulizing a liquid and dispersing it Within a gaseousmedium. More particularly, the present invention relates to improvementsin inhalation therapy so that oxygen, anaesthetic gases and similarinhalation mixtures intended for human respiration may be humidified toa considerably greater extent than is possible with known nebulizers,aspirators and the like. Known apparatus can at best humidify aninhalation mixture to 100% relative humidity with perhaps a very smallamount of water present in aerosol dispersion.

In normal human respiration air is inhaled at the temperature andrelative humidity of the surroundings. It is exhaled at approximatelybody temperature and 100% relative humidity containing a larger amountof water vapor than that present in the inhaled air. There is thus a netloss of water from the body during respiration. The above will becomemore apparent from a consideration of the water content of air inhaledat room temperature of about 70 F. and exhaled at normal bodytemperature at 98.6 F. The inhaled air has been warmed to bodytemperature and then exhaled saturated with water vapor at bodytemperature. If it is assumed that the room air at 70 F. is at 50%relative humidity, the air contains 11 milligrams of water vapor perliter of air. The exhaled air at 98.6% and 100% relative humidity, i.e.,saturated with water vapor, contains 44 milligrams per liter. It is thusapparent that for every liter of air inhaled and exhaled there is a netloss of 33 milligrams of water from the body. This is a 300% increase inwater content in the exhaled air over that present in the entering air.

Similarly, if the room air at 70 F. were at 100% relative humidity, itwould contain 22 milligrams of water vapor per liter. In this case, forevery liter of air used in respiration, there would be a net loss of 44minus 22 or 22 milligrams of water per liter of air. This is a 100%increase in the actual water content of the air.

The above noted water loss from the body cannot be stopped or decreasedby supplying air or oxygen substantially at body temperature of 98.6 F.and saturated with water vapor since in the case of air such a mixturewould be distressing to a healthy person, and especially distressing toa person having a respiratory disorder. A saturated oxygen-rich mixtureinhaled at body temperature would be intolerable to all.

The water given up to the air during respiration comes from the lungs.The mucous membranes lining the lungs are provided with cilia, smallhair like structures which are continuously in motion. There arehundreds of cilia per square micron of surface moving independently ofone another in a whip-like forward motion with a somewhat slower returnmore than 100 times a minute. The motion of the cilia propels a film ofliquid up and out of the lungs carrying airborne bacteria, dust and thelike, and thus constitutes one of the protective mechanisms of the humanbody. When the liquid film thickens, as is the case when there is asubstantial amount of water being lost to the air, the cilia havedifiiculty in propelling the liquid film. As the film further thickens,the protective mechanism stops operating and many undesirableconsequences can ensue, for example, postoperative pneumonia.

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One of the aims of the present invention is to control the fluidity ofthe liquid film within the lungs by stopping and/or decreasing the netwater loss from the body during respiration. The present inventionachieves the above by introducing a precisely controlled volume of steaminto a high velocity stream of air or other inhalation mixture to bemolecularly dispersed in the inhalation mixture. The quantity of steamintroduced is sufiicient to raise the total amount of water present toabout 44 milligrams of water per liter, which corresponds to the amountof water present in saturated air at body temperature. The mixture ofsteam in the inhalation mixture exists as a molecularly dispersedmixture for about 600 milliseconds and is a transient condition. Withinthis time, using a channel of small crosssection and low heatconductivity, the mixture can be supplied to the patient, and inhaledand warmed to body temperature already containing 44 milligrams of watervapor per liter of air. Starting with an inhalation mixture at initiallyapproximately 0% relative humidity, the addition of a volume percent ofsteam of about 3% is sufiicient to raise the water content to thedesired amount. The heat content of this small amount of superheatedsteam raises the temperature of the inhalation mixture only about 2 C.

One of the primary objects of the present invention is to provide animproved method of dispersing one fluid within another.

Another object of the present invention is to provide an improved methodof humidifying an inhalation mixture.

Still another object of the present invention is to provide apparatusfor humidifying an inhalation mixture to a considerably greater extentthan that achieved with prior art apparatus.

A further object of the present invention is to supply an inhalationmixture for respiration at about normal room temperature, and containingas a transient mixture an amount of water vapor approximatelycorresponding to the amount of water vapor present in the mixture whensubsequently exhaled at body temperature.

A still further object of the present invention is to provide apparatusfor producing a transient molecular dispersion of water vapor within aninhalation mixture which is substantially in excess of relativehumidity, relative to the ambient conditions.

These and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the drawings, wherein:

FIGURE 1 is a schematic illustration of the embodiment for carrying outthe present invention, and

FIGURE 2 is an end view of a self-contained unit including the elementsschematically illustrated in FIG- URE 1.

Referring now to the drawing, and more particularly to FIGURE 1, thereis shown a conduit 10 receiving an oxygen-rich inhalation mixture from asupply source schematically indicated by arrow 11, a flow meter 12, aflow control valve 13, an inhalation mixture supply conduit 14, a steamgenerator generally designated by reference numeral 15, a capillary tube16 leading from steam generator 15 to conduit 14, and a point ofrespiration indicated by a face mask 17.

Steam generator 15 includes an outer casing 18 forming a liquidreservoir 19 in the interior thereof and provided with an atmosphericvent 20. Casing 18 is preferably made of glass or other transparentmaterial so that the level of liquid reservoir 19 may be more readilychecked. A removable cover 21 closes off the top of casing 18. A syphontube 22 is mounted Within casing 18 by having its upper end secured to adepend- 3 ing flange portion 23 of cover 21 so that the lower end ofsyphon tube 22 extends down into reservoir 19 and terminates above thebottom of casing 18. A container 24 forming an enclosed vaporizationspace is mounted within syphon tube 22 by having portions thereofimbedded in flange portion 23, or by any other suitable means. Container24 which is shown as a cylinder is preferably made of a microporousceramic material such as that disclosed in my Patent No. 2,404,872,issued July 30, 1946, entitled, Method and Apparatus for Separatingimmiscible Fluids. The microporous ceramic material functions as a phaseseparator and permits water to flow through the micropores from syphontube 22 into the interior of container 24 but prevents steam pressuregenerated within container 24 from being exerted back into the waterwithin syphon tube 22.

The operation of syphon tube 22 and of cylinder 24 will become moreapparent from the following. An electric heating element 25 ispositioned within container 24 by any suitable means to vaporize waterentering container 24 via the micropores of the ceramic material. Thesteam generated is vented from container 24 through the capillary tube16. The steam pressure generated within container 24 may be of the orderof 50 millimeters of mercury above atmospheric pressure, and yet due tothe phase-separating characteristics of the microporous ceramic materialthis pressure would not be transmitted to the water within syphon tube22. However, the steam pressure is effective to pass steam throughcapillary tube 16 wherein the pressure is of the order of 20 millimetersof mercury above atmospheric pressure into the oxygenrich stream inconduit 14 which is maintained at a slightly lower pressure, forexample, millimeters above atmospheric pressure.

Due to the flow of water from syphon tube 22 into container 24 forvaporization therein, a suction is maintained in syphon tube 22 whichmaintains water in contact with the outside of the microporous ceramiccontainer 24 so long as the liquid level within reservoir 19 is abovethe lower end of syphon tube 22.

Heating element 25 is supplied with electrical energy via leads 26, 27connected to a suitable power supply 28. Arheostat 29 regulates thecurrent supplied to heater element 25 to provide a control over theamount of steam generated in cylinder 24 and supplied via capillary tube16 for injection into supply conduit 14 to form a molecularly dispersedtransient mixture substantially in excess of 100% relative humidity,relative to the ambient conditions. The amount of water vapor or steamgenerated is independent of the flow rate of the oxygen-rich, stream.Accordingly, the degree of humidification may be varied from nearly zeroto about 200% relative humidity depending upon the setting of rheostat29. A switch 30 enables an on and off control of heater element 25. Afuse 31, and a pilot light 32, which when lit signifies that the heateris in operation, are provided as safety features.

The above described steam generator is especially desirable since only afew cubic centimeters of water are being heated to boiling withincylinder 24 at any one time. This enables a fast start-up of theapparatus, and yet a constant supply of water through the micropores isassured. This is in contrast to a conventional steam boiler wherein alarge volume of water would be initially brought to the boiling pointbefore any steam would be generated. The steam generator of the presentinvention enables a more precise control of the output and requires onlya small current supply for heater 25. The micropores of cylinder 24 ineffect function as millions of boiler water feed pumps, withoutpulsation. While such a steam generator is preferred for the above notedreasons, it will be appreciated that any conventional steam generatormight be utilized in lieu thereof, although, not as advantageously.

Since as stated above, the molecularly dispersed mixture exists forabout 600 milliseconds, this is a critical lim- 4- itation since thesteam and gas mixture must be supplied for respiration before there isany considerable condensation of the steam. One skilled in the art andappraised of the significance of this time period may so correlate thelength of supply conduit 14 downstream of the capillary tube supplyingthe steam, the bore of conduit 14 and the gas velocities so that thetransient mixture is inhaled before condensation occurs to anyconsiderable extent. For example, it has been found experimentally thatthe velocity of a ten liter per'minute flow of gas is approximately 70feet per second in a one-eighth inch diameter A tube. With a velocity of70 feet per second, the flow would thus proceed through a five footlength of tube or pipe in second or about 70 milliseconds. As is knownin the art, the rate of flow in a tube or pipevaries inversely as thesquare of the diameter thereof. Consequently, a one inch diameter tubewould have a gas velocity which is approximately ,4 of 70 feet persecond with a ten liter per minute flow. Thus, variations in the presentinvention may readily be made in order to achieve certain desiredresults by simple calculations.

The humidified inhalation mixture can be supplied to l the face mask 17as shown, to a suifuser harness with plastic tubes entering thenostrils, to a nasal catheter, into a cap over a tracheotomy incision,directly into an incubator, or by other means.

FIGURE 2 illustrates that the above described elements may be allmounted within a small portable, selfcontained unit including a casing33 provided with an inlet connection 34 for conduit 10, an outletconnection 35 for conduit 14, and with apertures enabling flow meter 12,control valve 13, rheostat 29, switch 30, fuse 31, and pilot light 32 tobe accessible and visible from the outside.

The transient molecular dispersion of steam within an oxygen-richatmosphere has been demonstrated by means of apparatus having twostreams of dry oxygen each regulated by a flow meter and an associatedvalve. The flow meter of one stream is set to pass at 10 liters perminute through the humidifier of the present invention into atransparent enclosure containing a Serdex relative humidity indicator.The Serdex indicator initially records a reading of about 0% relativehumidity. The humidifier is then started and the relative humidity ofthe stream is brought up to The second stream is now connected into theline downstream of the humidifier and its flow is also set at 10 litersper minute. A thermostat regulating the electric heater element of thehumidifier of the present invention is adjusted to a higher setting sothat more steam is evolved. All of the humidity for both streams iscarried in the first stream from the humidifier to the point ofadmixture with the second stream. Eventually, the Serdex indicatorreading is approximately 100% relative humidity for the two combinedstreams. Therefore, it is apparent that the first stream carried a watervapor content equivalent to 200% relative humidity since the secondstream was entirely dry. The flow of the second stream is now stopped.Upon darkening the room and shining a light beam at right angles throughthe first stream it may be observed that the stream is optically empty,i.e., molecularly dispersed.

It will be appreciated that the present invention is susceptible to manychanges and modifications within the scope of the instant disclosure.For example, medication may be added to the inhalation mixture, and thehumidifier of the present invention may be utilized in conjunction withoxygen supplied to aviators or divers. Accordingly, I intend toencompass all such changes and modifications as are contained within thescope of the appended claims.

I claim:

1. Humidifier apparatus comprising a conduit supplying an oxygen-richgas stream intended for human respiration, means for metering the flowof said gas stream through said conduit, a steam generator, a capillarytube leading from said steam generator to said conduit to inject aquantity of water vapor into said gas stream to form a transientmolecularly dispersed mixture of said gas and water vapor, said mixturehaving a water vapor content corresponding approximately to the watercontent of said gas stream when saturated at body temperature, and meansfor delivering said mixture for respiration before any substantialcondensation of the water vapor in said mixture occurs.

2. The humidifier apparatus as defined in claim 1, wherein said mixturehas a water vapor content of approximately 44 milligrams of water perliter of gas.

3. Apparatus as defined in claim 1, wherein said steam generatorcomprises an outer casing forming a liquid reservoir, a syphon tubesecured within said casing and having its lower end extending beneaththe liquid level in said reservoir, a cylinder of a microporous ceramicmaterial mounted within said syphon tube to permit water to flow intothe interior of said cylinder, and an electric heating element Withinsaid cylinder for vaporizing water therein.

4. Humidifier apparatus for humidifying an inhalation mixture comprisinga supply source of a gas intended for human respiration, a conduitleading from said source, means for metering the flow of said gas streamthrough said conduit, a steam generator including heater means andcontrol means for said heater means, a capillary tube leading from saidstream generator to said conduit to inject a predetermined quantity ofwater vapor into said gas stream to form a transient molecularlydispersed mixture of said gas and water vapor, said mixture having aWater vapor content corresponding approximately to the Water content ofsaid gas stream when saturated at body temperature, and means fordelivering said mixture for respiration before any substantialcondensation of the water vapor in said mixtureoccurs.

5. The humidifier apparatus as defined in claim 4 wherein said mixturehas a water vapor content of approximately 44 milligrams of water perliter of gas.

6. A steam generator comprising an outer casing forming a liquidreservoir, a syphon tube secured within said casing and having its lowerend extending beneath the liquid level in said reservoir, a cylinder ofa microporous ceramic material mounted within said syphon tube to permitwater to flow into the interior of said cylinder, an electric heatingelement within said cylinder for vaporizing water therein, and a steamdischarge tube leading from said cylinder.

7. A steam generator comprising an outer casing forming a liquidreservoir, a cylinder having wall portions of a microporous materialmounted within said reservoir to permit water to flow therethrough intothe interior thereof, and to prevent steam pressure within said cylinderfrom being transmitted therethrough, a heating element within saidcylinder for vaporizing water therein, and means for discharging steamfrom said cylinder.

8. A steam generator comprising an outer casing forming aliquidreservoir, a syphon tube secured within said casing and having itslower end positioned within said reservoir, a cylinder having wallportions of a microporous material mounted within said syphon tube topermit water to flow therethrough into the interior thereof and toprevent steam pressure within said cylinder from being transmittedtherethrough, a heating element within said cylinder for vaporizingwater therein, and means for discharging steam from said cylinder.

9. A method for humidifying a gas stream intended for human respirationwhich comprises regulating the quantity and velocity of said gas stream,injecting a predetermined small amount of steam into said gas stream toform a transient molecularly dispersed mixture of said gas and watervapor, said mixture having a water vapor content correspondingapproximately to the water content of said gas stream when saturated atbody temperature, and delivering said mixture for respiration prior toany substantial condensation of the water vapor in said mixture.

10. The method of claim 9, wherein said mixture has a water vaporcontent of approximately 44 milligrams of water per liter of gas.

.11. A method for humidifying a gas stream intended for humanrespiration which comprises regulating the quantity and velocity of saidgas stream, injecting a predetermined small amount of steam into saidgas stream to form a transient molecularly dispersed mixture of said gasand water vapor, said mixture having a water vapor content correspondingapproximately to the water content of said gas stream when saturated atbody temperature, and delivering said mixture for respiration within 600milliseconds after its formation.

12. The method of claim 11, wherein said gas stream is an oxygen-richgas stream.

13. A method for humidifying an oxygen-rich gas stream intended forhuman respiration which comprises regulating the quantity and velocityof said gas stream, injecting a predetermined small amount ofsuper-heated steam into said gas stream to form a transient molecularlydispersed mixture of said gas and water vapor, said mixture having awater vapor content of approximately 44 milligrams of Water per liter ofgas, and delivering said mixture for respiration prior to anysubstantial condensation of the water vapor in said mixture.

14. The method of claim 13, wherein said mixture is delivered forrespiration within 600 milliseconds after its formation.

References Cited by the Examiner UNITED STATES PATENTS 680,122 8/1901Camp 2l-1l7 2,023,324 12/1935 Johnson et al. 128-192 2,368,115 1/1945Chapple 128192 2,547,865 4/1951 Hanks.

2,709,577 5/1955 Pohndorf et a1. 128-185 2,778,617 1/1957 Gibbon 128191I 2,806,932 9/1957 Conlin et al.,

2,812,762 '11/l957 Jordan et al. 128l9l 2,847,548 8/ 1958 Gordon et a1.

RICHARD A. GAUDET, Primary Examiner. JORDAN FRANKLIN, Examiner.

R. D. TEGTMEYER, D. S. BURKS, W. E. KAMM, Assistant Examiners.

1. HUMIDIFIER APPARATUS COMPRISING A CONDUIT SUPPLYING AN OXYGEN-RICHGAS STREAM INTENDED FOR HUMAN RESPIRATION MEANS FOR METERING THE FLOW OFSAID GAS STREAM THROUGH SAID CONDUIT, A STREAM GENERATOR, A CAPILLARYTUBE LEADING FROM SAID STREAM GENERATOR TO SAID CONDUIT TO INJECT AQUANTITY OF WATER VAPOR INTO SAID GAS STREAM TO FORM A TRANSIENTMOLLECULARLY DISPERSED MIXTURE OF SAID GAS AND WATER VAPOR SAID MIXTUREHAVING A WATER VAPOR